The present invention relates to check valve assemblies that provide enhanced protection against unwanted reverse flow through conduits.
A check valve is a type of valve that permits flow of a fluid in one direction while inhibiting reverse flow. Such valves are typically used to prevent contamination of plumbing systems. "Duckbilled" type check valves usually have a cylindrical base/inlet end that fits snugly into a conduit through which the fluid will be flowing. The outlet end of the valve tapers somewhat like the bill of a duck. There is a central bore extending through the valve between the entry and outlet. Normal fluid flow drives the flexible bill open to permit flow through the valve. Reverse flow drives the bill closed.
Prior art duckbilled check valves are available from many suppliers. Three such suppliers are Vernay Laboratories, Eagle-Picher and Moxness.
While duckbilled check valves have been used in a wide variety of applications, they are particularly well suited for use in nozzle assemblies that assist in dispensing actives (e.g. cleaners, fertilizers, herbicides, pesticides) from the end of a garden hose. See e.g. check valve 15 in U.S. Pat. No. 5,906,316. The disclosure of this patent and of all other publications referred to herein are incorporated by reference as if fully set forth herein.
However, some municipalities have recently enacted codes that require effective back flow protection even where a check valve is exposed to water supplies that contain grit or small rock fragments. The concern of these codes is that such solid materials may cause conventional check valves to temporarily jam in the open position (and thereby defeat the back flow protection of the valve before fluid flow can dislodge the blockage).
Multiple in-line check valves has been proposed to comply with the requirements of these codes (with the check valves spaced apart about a centimeter or so, in order that the valves not interfere with each other). While such structures would enhance back flow protection, they would render the portion of the ultimate product that contains this protection more bulky. This is a particular problem with compact structures such as garden hose outlet nozzles. Further, installing separate multiple check valves in such nozzles requires multiple installation operations, and may also require modification to the ultimate product (or additional components) to retain the check valves in an appropriately spaced configuration.
There is therefore a need for improved check valve assemblies.